44i Bootis:
The Terrible Twos: What Might Happen If Our Sun Had A Twin

Credit: NASA/CXC/M.Weiss

This artist's conception depicts the two closely
orbiting stars of 44i Bootis. These two stars circle
around each other at a rapid rate, passing in front of
one another every three hours. The red arrow in the
illustration indicates the direction that the stars are
orbiting.

The plots to the right show Chandra data on X-ray
emission from Neon ions. The 4 panels show the shift in
wavelength at which the Neon X-ray emission peaks as
the stars orbit one another. By using the Doppler
effectthe same process that causes the frequency
of an ambulance's siren to shift up and down as the
ambulance approaches and recedesastronomers were
able to pinpoint the location of the source of most of
the X-rays. They found to their surprise that the large
white spot on the larger star produces at least half of
the X-rays from this system. In contrast, the X-ray
active regions on our Sun tend to be near the
equator.